The present invention relates to a novel thermoplastic resin composition and more particularly to a thermoplastic resin composition well-balanced in rigidity, impact resistance, flexibility and processability.
Thermoplastic resins are utilized in various industrial fields as materials superior in moldability. Besides, their utilization fields have been expanded by being blended for modification with resins having various properties and fillers. It is also well known that effects of such blending, for example, improvement of impact resistance and that of heat resistance are attained by dynamically heat-treating the resulting mixtures. As the method for dynamically heat-treating a thermoplastic resin substantially not having an unsaturated carbon-carbon bond it is known to utilize an organic peroxide. However, as to compositions obtained by such method utilizing organic peroxides, improvements have been desired in the following points.
As exemplified in Japanese Patent Publication No. 34210/1978 (U.S. Pat. No. 3,806,558), since a free radical initiator typified by an organic peroxide is used, there is obtained a composition which exhibits good fluidity in injection molding in the case where the thermoplastic resin used is an organic peroxide non-crosslinked type resin such as a polypropylene resin, but the organic peroxide remaining in the composition deteriorates the thermal stability and weathering resistance of the composition and there occurs a thermal decomposition of the organic peroxide rapidly, resulting in that a molecular cutting reaction is unavoidable, thus leading to deterioration of mechanical characteristics such as yield strength, bending strength, and flexural modulus. Moreover, in the case where the composition is used in extrusion or blow molding, there arise problems such as deterioration of drawdown resistance, and surface roughening and insufficient elongation of parison. Also in injection modling the gloss of the resulting molded product is poor, thus affecting the beaty of the commodity. Organic peroxide crosslinked type resins such as polyethylene resins are either unemployable because of marked deterioration in fluidity of the composition obtained or require the use of an extremely small amount of an organic peroxide, thus it is difficult to handle them. Further, when the above conventional method is used, there inevitably arise such problems as poor stability and safety of the free radical forming agent during storage and dynamic treatment thereof, as well as thermal decomposition loss due to the adhesion to heated inner walls of a processing machine.
It is an object of the present invention to overcome the above-mentioned problems of the prior art.
It is another object of the present invention to provide an improved thermoplastic resin composition by crosslinking a thermoplastic resin using a crosslinking reaction as a drawback of conventional organic peroxides and which was found out by the present inventors.